No Oil Substitutes
Gold - The yellow metal holds a unique status in everything from religion to jewelry to wealth storage. Even central banks and world governments look to gold as an inflation hedge and trade gold in times of economic trouble (2016 - Venezuela); no other metal enjoys this distinction not even platinum and there's no reason to think that will change anytime soon. The last time fiat currency wasn't being used world trade relied fundamentally on the gold standard. With the US dollar losing popularity as the world reserve currency and China looking to gold to prop up its own currency it appears as if the gold standard will once again run the world economic system.
Oil production still powers the economies of many key nations
And these are nations of influence - Saudi Arabia, Russia, Iran, Canada, United States. Other key countries such as Nigeria and Venezuela are developing vast oil reserves as a source of future economic growth. As long as oil is available there will be a market for it. (nigeria oil reserves)
Renewable Energy Sources Continue To Be Too Expensive
With the world economy slumping along there is no reason to expect people to voluntarily shift to expensive sources of energy anytime soon. Even the cheapest of these - energy derived from corn (corn demand, ethanol) in South America - is already wreaking havoc on commodity prices in that part of the world because it takes too much of the crop to replace just a fraction of the energy it needs.